The present invention relates generally to optical fibers that are embedded in structures and, more specifically, to a method for attaching optical connectors to such embedded fibers.
Optical fibers may be embedded in many types of structural members. Systems having embedded optical fibers may detect damage or strain in aircraft, ground and water vehicles, and non-movable structures. In such systems, an optical signal is injected at one end of the fiber. A sensor is positioned either at the other end of the fiber or, if the other end is reflective, at the same end at which the signal is injected. Changes in intensity and travel time of the injected signal can be measured to determine the extent and location of the damage in the structure. The fibers may be arranged in a matrix shape to enhance localization of the damage, as disclosed in U.S. Pat. No. 4,581,527 issued to Crane et al.
In addition, embedded optical fibers may be used for communication between electronic systems, as is common in aircraft.
Optical fibers may be embedded in composite laminate structures, as disclosed in U.S. Pat. No. 4,772,092 issued to Hofer et al. and in U.S. Pat. No. 4,537,469 issued to Kircher et al. In composite laminate structures, the optical fibers may be placed between laminate layers or may be integral to the woven matting or "pre-preg" that forms the laminate layers. The matting may consist of fibers made of glass, graphite, boron, KEVLAR, or other suitable materials. The matting layers are commonly bound together with a resin binder, such as epoxy.
Optical fibers may be embedded not only in composite laminate structures, but may also be embedded in many types of resins, plastics, epoxies, metals, and other materials. For example, U.S. Pat. No. 4,950,043 issued to Russom discloses a method for embedding optical fibers in titanium.
Methods known in the art for fabricating structural members having embedded optical fibers commonly leave a portion of each embedded fiber protruding beyond the edge of the structural member. An optical connector may then be attached to this protruding fiber portion. Not only is aligning a connector with a dangling fiber portion a difficult task, but the structural member must be carefully handled during manufacturing and installation to avoid damaging the protruding fiber portions. Breakage of a protruding fiber portion may make it impossible to attach a connector to it using methods known in the art and may render the entire structural member unusable.
Although the protruding portions of fibers embedded in all types of structures are susceptible to damage, the protruding portions of fibers embedded in composite laminate structures are particularly susceptible to damage because they are cured in an autoclave at a high temperature, which vaporizes some or all of the cladding layer of the protruding fiber portions, making them quite brittle.
A method for attaching a connector to an embedded optical fiber that does not risk rendering the fiber or structure unusable would be highly desirable. These problems and deficiencies are clearly felt in the art and are solved by the present invention in the manner described below.